U.S. patent application number 14/319434 was filed with the patent office on 2015-12-03 for noise detection and mitigation for capacitive sensing devices.
The applicant listed for this patent is Synaptics Incorporated. Invention is credited to Luen-Ming SHEN.
Application Number | 20150346859 14/319434 |
Document ID | / |
Family ID | 54701695 |
Filed Date | 2015-12-03 |
United States Patent
Application |
20150346859 |
Kind Code |
A1 |
SHEN; Luen-Ming |
December 3, 2015 |
NOISE DETECTION AND MITIGATION FOR CAPACITIVE SENSING DEVICES
Abstract
Techniques, including a method, for detecting an input object.
The method includes driving sensing signals onto and receiving
resulting signals with a first plurality of sensor electrodes and a
second plurality of sensor electrodes to determine first changes of
capacitance between the first plurality of sensor electrodes and an
input object and the second plurality of sensor electrodes and the
input object. The method also includes driving the first plurality
of sensor electrodes with transmitter signals and receiving
resulting signals with the second plurality of sensor electrodes to
determine second changes of capacitance between the first plurality
of sensor electrodes and the second plurality of sensor electrodes.
The method further includes entering a high noise mode based on a
comparison between the first changes of capacitance and the second
changes of capacitance.
Inventors: |
SHEN; Luen-Ming; (Taipei,
TW) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Synaptics Incorporated |
San Jose |
CA |
US |
|
|
Family ID: |
54701695 |
Appl. No.: |
14/319434 |
Filed: |
June 30, 2014 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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62007277 |
Jun 3, 2014 |
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Current U.S.
Class: |
345/174 |
Current CPC
Class: |
G06F 3/0418 20130101;
G01V 3/10 20130101; G06F 3/0445 20190501; G06F 3/0443 20190501 |
International
Class: |
G06F 3/044 20060101
G06F003/044; G01V 3/08 20060101 G01V003/08 |
Claims
1. A method for detecting an input object, the method comprising:
driving sensing signals onto and receiving resulting signals with a
first plurality of sensor electrodes and a second plurality of
sensor electrodes to determine first changes of capacitance between
the first plurality of sensor electrodes and the input object and
the second plurality of sensor electrodes and the input object;
driving the first plurality of sensor electrodes with transmitter
signals and receiving resulting signals with the second plurality
of sensor electrodes to determine second changes of capacitance
between the first plurality of sensor electrodes and the second
plurality of sensor electrodes; and entering a high noise mode
based on a comparison between the first changes of capacitance and
the second changes of capacitance.
2. The method of claim 1, further comprising; generating a
predicted location of the input object based on previous locations
of the input object.
3. The method of claim 2, further comprising: rejecting a candidate
location of the input object based on the first changes of
capacitance, the predicted location, and the second changes of
capacitance.
4. The method of claim 3, wherein rejecting the candidate location
comprises: correlating a first set of object locations based on the
predicted location and the first changes in capacitance with a
second set of object locations based on the second changes in
capacitance.
5. The method of claim 4, wherein correlating the first set of
object locations with the second set of object locations comprises:
determining that the first set of object locations does not include
the same object locations as the second set of object
locations.
6. The method of claim 1, wherein the high noise mode comprises:
foregoing reporting an object location until a confidence threshold
for that object location is reached.
7. The method of claim 1, wherein the high noise mode comprises:
suspending baseline relaxation.
8. The method of claim 1 wherein driving the first plurality of
sensor electrodes comprises: driving a subset of the first
plurality of sensor electrodes, where each sensor electrode in the
subset is proximate to a sensor electrode for which the first
changes of capacitance indicate presence of the input object.
9. The method of claim 8, wherein driving the first plurality of
sensor electrodes further comprises: increasing a burst count
relative to a commonly used burst count for transcapacitive
sensing.
10. A processing system for operating an input device for
capacitive sensing, the processing system comprising: a sensor
module configured to: drive sensing signals onto and receive
resulting signals with a first plurality of sensor electrodes and a
second plurality of sensor electrodes to determine first changes of
capacitance between the first plurality of sensor electrodes and an
input object and the second plurality of sensor electrodes and the
input object, and drive the first plurality of sensor electrodes
with transmitter signals and receive resulting signals with the
second plurality of sensor electrodes to determine second changes
of capacitance between the first plurality of sensor electrodes and
the second plurality of sensor electrodes; and a noise reduction
module configured to: enter a high noise mode based on a comparison
between the first changes of capacitance and the second changes of
capacitance.
11. The processing system of claim 10, wherein the noise reduction
module is further configured to: generate a predicted location of
the input object based on previous locations of the input
object.
12. The processing system of claim 11, wherein the noise reduction
module is further configured to: reject a candidate location of the
input object based on the first changes of capacitance, the
predicted location, and the second changes of capacitance.
13. The processing system of claim 12, wherein the noise reduction
module is configured to reject the candidate location by:
correlating a first set of object locations based on the predicted
location and the first changes in capacitance with a second set of
object locations based on the second changes in capacitance.
14. The processing system of claim 13, wherein the noise reduction
module is configured to correlate the first set of object locations
with the second set of object locations by: determining that the
first set of object locations does not include the same object
locations as the second set of object locations.
15. The processing system of claim 10, wherein, in the high noise
mode, the noise reduction module is configured to: forego reporting
an object location until a confidence threshold for that object
location is reached.
16. The processing system of claim 10, wherein, in the high noise
mode, the noise reduction module is configured to: suspending
baseline relaxation.
17. The processing system of claim 10 wherein the noise reduction
module is configured to cause the sensor module to drive the first
plurality of sensor electrodes with transmitter signals and receive
resulting signals with the second plurality of sensor electrodes
by: causing the sensor module to drive a subset of the first
plurality of sensor electrodes, where each sensor electrode in the
subset is proximate to a sensor electrode for which the first
changes of capacitance indicate presence of the input object.
18. The processing system of claim 17, wherein the noise reduction
module is configured to cause the sensor module to drive sensing
signals onto and receive resulting signals with the first plurality
of sensor electrodes and the second plurality of sensor electrodes
by: causing the sensor module to increase a burst count relative to
a commonly used burst count for transcapactive sensing.
19. An input device, comprising: a first plurality of sensor
electrodes; a second plurality of sensor electrodes; and a
processing system, comprising: a sensor module configured to: drive
sensing signals onto and receive resulting signals with a first
plurality of sensor electrodes and a second plurality of sensor
electrodes to determine first changes of capacitance between the
first plurality of sensor electrodes and an input object and the
second plurality of sensor electrodes and the input object, and
drive the first plurality of sensor electrodes with transmitter
signals and receive resulting signals with the second plurality of
sensor electrodes to determine second changes of capacitance
between the first plurality of sensor electrodes and the second
plurality of sensor electrodes; and a nose reduction module
configured to: enter a high noise mode based on a comparison
between the first changes of capacitance and the second changes of
capacitance.
20. The input device of claim 19, wherein the noise reduction
module is further configured to: reject a candidate location of the
input object based on the first changes of capacitance, a predicted
location, and the second changes of capacitance.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application claims the priority benefit of U.S.
provisional patent application Ser. No. 62/007,277, filed Jun. 3,
2014 and titled, "Interference Detection via Absolute Capacitive
Sensing." The subject matter of this related application is hereby
incorporated herein by reference.
BACKGROUND
[0002] 1. Technical Field
[0003] Embodiments of the present invention generally relate to a
method and apparatus for capacitive sensing, and more specifically,
to noise detection and mitigation for capacitive sensing
devices.
[0004] 2. Description of the Related Art
[0005] Input devices including proximity sensor devices (also
commonly called touchpads or touch sensor devices) are widely used
in a variety of electronic systems. Proximity sensor devices may be
used to provide interfaces for the electronic system. For example,
proximity sensor devices are often used as input devices for larger
computing systems (such as opaque touchpads integrated in, or
peripheral to, notebook or desktop computers). Proximity sensor
devices are also often used in smaller computing systems (such as
touch screens integrated in cellular phones).
[0006] Environmental noise may affect the signals received while
operating a proximity sensor device for capacitive sensing. More
specifically, various noise signals, such as ambient signals or
signals generated by various elements of the proximity sensor
device may affect signals received during capacitive sensing. These
noise signals may cause the proximity sensor device to incorrectly
identify the presence of one or more input objects.
[0007] As the foregoing illustrates, what is needed in the art are
techniques and apparatus for reducing the impact of environmental
noise on proximity sensor devices.
SUMMARY
[0008] One implementation of the present disclosure includes a
method for detecting an input object. The method includes driving
sensing signals onto and receiving resulting signals with a first
plurality of sensor electrodes and a second plurality of sensor
electrodes to determine first changes of capacitance between the
first plurality of sensor electrodes and an input object and the
second plurality of sensor electrodes and the input object. The
method also includes driving the first plurality of sensor
electrodes with transmitter signals and receiving resulting signals
with the second plurality of sensor electrodes to determine second
changes of capacitance between the first plurality of sensor
electrodes and the second plurality of sensor electrodes. The
method further includes entering a high noise mode based on a
comparison between the first changes of capacitance and the second
changes of capacitance.
[0009] Another implementation of the present disclosure includes a
processing system. The processing system includes a sensor module
and a noise reduction module. The sensor module is configured to
drive sensing signals onto and receive resulting signals with a
first plurality of sensor electrodes and a second plurality of
sensor electrodes to determine first changes of capacitance between
the first plurality of sensor electrodes and an input object and
the second plurality of sensor electrodes and the input object. The
sensor module is also configured to drive the first plurality of
sensor electrodes with transmitter signals and receive resulting
signals with the second plurality of sensor electrodes to determine
second changes of capacitance between the first plurality of sensor
electrodes and the second plurality of sensor electrodes. The noise
reduction module is configured to enter a high noise mode based on
a comparison between the first changes of capacitance and the
second changes of capacitance.
[0010] Another implementation of the present disclosure includes an
input device. The input device includes a first plurality of sensor
electrodes, a second plurality of sensor electrodes, and a
processing system. The processing system includes a sensor module
and a noise reduction module. The sensor module is configured to
drive sensing signals onto and receive resulting signals with a
first plurality of sensor electrodes and a second plurality of
sensor electrodes to determine first changes of capacitance between
the first plurality of sensor electrodes and an input object and
the second plurality of sensor electrodes and the input object. The
sensor module is also configured to drive the first plurality of
sensor electrodes with transmitter signals and receive resulting
signals with the second plurality of sensor electrodes to determine
second changes of capacitance between the first plurality of sensor
electrodes and the second plurality of sensor electrodes. The noise
reduction module is configured to enter a high noise mode based on
a comparison between the first changes of capacitance and the
second changes of capacitance.
BRIEF DESCRIPTION OF THE DRAWINGS
[0011] So that the manner in which the above recited features of
the present invention can be understood in detail, a more
particular description of the invention, briefly summarized above,
may be had by reference to embodiments, some of which are
illustrated in the appended drawings. It is to be noted, however,
that the appended drawings illustrate only typical embodiments of
this invention and are therefore not to be considered limiting of
its scope, for the invention may admit to other equally effective
embodiments.
[0012] FIG. 1 is a schematic block diagram of an input device
integrated into an exemplary display device, according to one
example described herein.
[0013] FIG. 2 illustrates a simplified exemplary array of sensor
elements that may be used in the input device of FIG. 1, according
to one example described herein.
[0014] FIG. 3 illustrates "ghost objects" detected in the sensing
region of FIG. 1, according to one example described herein.
[0015] FIG. 4 illustrates a prediction operation for predicting an
object location, according to one example described herein.
[0016] FIG. 5 is a flow diagram of method steps for operating the
input device of FIG. 1 in noise detection mode, according to one
example described herein.
[0017] To facilitate understanding, identical reference numerals
have been used, where possible, to designate identical elements
that are common to the figures. It is contemplated that elements
disclosed in one embodiment may be beneficially utilized on other
embodiments without specific recitation. The drawings referred to
here should not be understood as being drawn to scale unless
specifically noted. Also, the drawings are often simplified and
details or components omitted for clarity of presentation and
explanation. The drawings and discussion serve to explain
principles discussed below, where like designations denote like
elements.
DETAILED DESCRIPTION
[0018] The following detailed description is merely exemplary in
nature and is not intended to limit the disclosure or its
application and uses. Furthermore, there is no intention to be
bound by any expressed or implied theory presented in the preceding
technical field, background, brief summary or the following
detailed description.
[0019] Various examples of the present technology provide an input
device with a noise reduction module for reducing the impact of
noise on input objects detected by an input sensing device. The
noise reduction module is configured to operate sensor electrodes
in the input device for capacitive sensing in an absolute sensing
mode and in a transcapacitive sensing mode, and also to predict
object locations based on previously detected input objects. The
noise reduction module is further configured to compare the results
generated in these sensing modes and the prediction results and to
remove object location data about sensed objects that are
determined to be insufficiently reliable. More specifically,
sensing is done in both absolute capacitive and transcapacitive
mode and the results are compared for inconsistencies. Object
locations that are detected in one sensing mode but not another may
be deemed unreliable and corresponding data removed. If any object
location data are removed in this manner, the noise reduction
module is also configured to enter a high noise mode, in which
further analysis is performed on the sensing and prediction
results, and in which further object location data may be
removed.
[0020] Turning now to the figures, FIG. 1 is a block diagram of an
exemplary input device 100, in accordance with embodiments of the
invention. In various embodiments, the input device 100 comprises a
sensing device and optionally a display device. In other
embodiments, the input device 100 comprises a display device having
an integrated sensing device, such as a capacitive sensing device.
The input device 100 may be configured to provide input to an
electronic system (not shown). As used in this document, the term
"electronic system" (or "electronic device") broadly refers to any
system capable of electronically processing information. Some
non-limiting examples of electronic systems include personal
computers of all sizes and shapes, such as desktop computers,
laptop computers, netbook computers, tablets, web browsers, e-book
readers, and personal digital assistants (PDAs). Additional example
electronic systems include composite input devices, such as
physical keyboards that include input device 100 and separate
joysticks or key switches. Further example electronic systems
include peripherals such as data input devices (including remote
controls and mice), and data output devices (including display
screens and printers). Other examples include remote terminals,
kiosks, and video game machines (e.g., video game consoles,
portable gaming devices, and the like). Other examples include
communication devices (including cellular phones, such as smart
phones), and media devices (including recorders, editors, and
players such as televisions, set-top boxes, music players, digital
photo frames, and digital cameras). Additionally, the electronic
system could be a host or a slave to the input device.
[0021] The input device 100 can be implemented as a physical part
of the electronic system, or can be physically separate from the
electronic system. As appropriate, the input device 100 may
communicate with parts of the electronic system using any one or
more of the following: buses, networks, and other wired or wireless
interconnections. Examples include I.sup.2C, SPI, PS/2, Universal
Serial Bus (USB), Bluetooth, RF, and IRDA.
[0022] In FIG. 1, the input device 100 is shown as a proximity
sensor device (also often referred to as a "touchpad" or a "touch
sensor device") configured to sense input provided by one or more
input objects 140 in a sensing region 120. Example input objects
include fingers and styli, as shown in FIG. 1.
[0023] Sensing region 120 encompasses any space above, around, in
and/or near the input device 100 in which the input device 100 is
able to detect user input (e.g., user input provided by one or more
input objects 140). The sizes, shapes, and locations of particular
sensing regions may vary widely from embodiment to embodiment. In
some embodiments, the sensing region 120 extends from a surface of
the input device 100 in one or more directions into space until
signal-to-noise ratios prevent sufficiently accurate object
detection. The distance to which this sensing region 120 extends in
a particular direction, in various embodiments, may be on the order
of less than a millimeter, millimeters, centimeters, or more, and
may vary significantly with the type of sensing technology used and
the accuracy desired. Thus, some embodiments sense input that
comprises no contact with any surfaces of the input device 100,
contact with an input surface (e.g. a touch surface) of the input
device 100, contact with an input surface of the input device 100
coupled with some amount of applied force or pressure, and/or a
combination thereof. In various embodiments, input surfaces may be
provided by surfaces of casings within which the sensor electrodes
reside, by face sheets applied over the sensor electrodes or any
casings, etc. In some embodiments, the sensing region 120 has a
rectangular shape when projected onto an input surface of the input
device 100.
[0024] The input device 100 may utilize any combination of sensor
components and sensing technologies to detect user input in the
sensing region 120. The input device 100 comprises one or more
sensing elements for detecting user input. As several non-limiting
examples, the input device 100 may use capacitive, elastive,
resistive, inductive, magnetic, acoustic, ultrasonic, and/or
optical techniques.
[0025] Some implementations are configured to provide images that
span one, two, three, or higher dimensional spaces. Some
implementations are configured to provide projections of input
along particular axes or planes.
[0026] In some resistive implementations of the input device 100, a
flexible and conductive first layer is separated by one or more
spacer elements from a conductive second layer. During operation,
one or more voltage gradients are created across the layers.
Pressing the flexible first layer may deflect it sufficiently to
create electrical contact between the layers, resulting in voltage
outputs reflective of the point(s) of contact between the layers.
These voltage outputs may be used to determine positional
information.
[0027] In some inductive implementations of the input device 100,
one or more sensing elements pick up loop currents induced by a
resonating coil or pair of coils. Some combination of the
magnitude, phase, and frequency of the currents may then be used to
determine positional information.
[0028] In some capacitive implementations of the input device 100,
voltage or current is applied to create an electric field. Nearby
input objects cause changes in the electric field, and produce
detectable changes in capacitive coupling that may be detected as
changes in voltage, current, or the like.
[0029] Some capacitive implementations utilize arrays or other
regular or irregular patterns 150 of capacitive sensing elements to
create electric fields. In some capacitive implementations,
separate sensing elements may be ohmically shorted together to form
larger sensor electrodes. Some capacitive implementations utilize
resistive sheets, which may be uniformly resistive.
[0030] Some capacitive implementations utilize "self capacitance"
(or "absolute capacitance") sensing methods based on changes in the
capacitive coupling between sensor electrodes and an input object.
In various embodiments, an input object near the sensor electrodes
alters the electric field near the sensor electrodes, thus changing
the measured capacitive coupling. In one implementation, an
absolute capacitance sensing method operates by modulating sensor
electrodes with respect to a reference voltage (e.g. system
ground), and by detecting the capacitive coupling between the
sensor electrodes and input objects.
[0031] Some capacitive implementations utilize "mutual capacitance"
(or "transcapacitance") sensing methods based on changes in the
capacitive coupling between sensor electrodes. In various
embodiments, an input object near the sensor electrodes alters the
electric field between the sensor electrodes, thus changing the
measured capacitive coupling. In one implementation, a
transcapacitive sensing method operates by detecting the capacitive
coupling between one or more transmitter sensor electrodes (also
"transmitter electrodes" or "transmitters") and one or more
receiver sensor electrodes (also "receiver electrodes" or
"receivers"). Transmitter sensor electrodes may be modulated
relative to a reference voltage (e.g., system ground) to transmit
transmitter signals. Receiver sensor electrodes may be held
substantially constant relative to the reference voltage to
facilitate receipt of resulting signals. A resulting signal may
comprise effect(s) corresponding to one or more transmitter
signals, and/or to one or more sources of environmental
interference (e.g. other electromagnetic signals). Sensor
electrodes may be dedicated transmitters or receivers, or may be
configured to both transmit and receive.
[0032] In FIG. 1, a processing system 110 is shown as part of the
input device 100. The processing system 110 is configured to
operate the hardware of the input device 100 to detect input in the
sensing region 120. The processing system 110 comprises parts of or
all of one or more integrated circuits (ICs) and/or other circuitry
components. For example, a processing system for a mutual
capacitance sensor device may comprise transmitter circuitry
configured to transmit signals with transmitter sensor electrodes,
and/or receiver circuitry configured to receive signals with
receiver sensor electrodes). In some embodiments, the processing
system 110 also comprises electronically-readable instructions,
such as firmware code, software code, and/or the like. In some
embodiments, components composing the processing system 110 are
located together, such as near sensing element(s) of the input
device 100. In other embodiments, components of processing system
110 are physically separate with one or more components close to
sensing element(s) of input device 100, and one or more components
elsewhere. For example, the input device 100 may be a peripheral
coupled to a desktop computer, and the processing system 110 may
comprise software configured to run on a central processing unit of
the desktop computer and one or more ICs (perhaps with associated
firmware) separate from the central processing unit. As another
example, the input device 100 may be physically integrated in a
phone, and the processing system 110 may comprise circuits and
firmware that are part of a main processor of the phone. In some
embodiments, the processing system 110 is dedicated to implementing
the input device 100. In other embodiments, the processing system
110 also performs other functions, such as operating display
screens, driving haptic actuators, etc.
[0033] The processing system 110 may be implemented as a set of
modules that handle different functions of the processing system
110. Each module may comprise circuitry that is a part of the
processing system 110, firmware, software, or a combination
thereof. In various embodiments, different combinations of modules
may be used. Example modules include hardware operation modules for
operating hardware such as sensor electrodes and display screens,
data processing modules for processing data such as sensor signals
and positional information, and reporting modules for reporting
information. Further example modules include sensor operation
modules configured to operate sensing element(s) to detect input,
identification modules configured to identify gestures such as mode
changing gestures, and mode changing modules for changing operation
modes.
[0034] In some embodiments, the processing system 110 responds to
user input (or lack of user input) in the sensing region 120
directly by causing one or more actions. Example actions include
changing operation modes, as well as GUI actions such as cursor
movement, selection, menu navigation, and other functions. In some
embodiments, the processing system 110 provides information about
the input (or lack of input) to some part of the electronic system
(e.g. to a central processing system of the electronic system that
is separate from the processing system 110, if such a separate
central processing system exists), In some embodiments, some part
of the electronic system processes information received from the
processing system 110 to act on user input, such as to facilitate a
full range of actions, including mode changing actions and GUI
actions.
[0035] For example, in some embodiments, the processing system 110
operates the sensing element(s) of the input device 100 to produce
electrical signals indicative of input (or lack of input) in the
sensing region 120. The processing system 110 may perform any
appropriate amount of processing on the electrical signals in
producing the information provided to the electronic system. For
example, the processing system 110 may digitize analog electrical
signals obtained from the sensor electrodes. As another example,
the processing system 110 may perform filtering or other signal
conditioning. As yet another example, the processing system 110 may
subtract or otherwise account for a baseline, such that the
information reflects a difference between the electrical signals
and the baseline. As yet further examples, the processing system
110 may determine positional information, recognize inputs as
commands, recognize handwriting, and the like.
[0036] "Positional information" as used herein broadly encompasses
absolute position, relative position, velocity, acceleration, and
other types of spatial information. Exemplary "zero-dimensional"
positional information includes near/far or contact/no contact
information. Exemplary "one-dimensional" positional information
includes positions along an axis. Exemplary "two-dimensional"
positional information includes motions in a plane. Exemplary
"three-dimensional" positional information includes instantaneous
or average velocities in space. Further examples include other
representations of spatial information. Historical data regarding
one or more types of positional information may also be determined
and/or stored, including, for example, historical data that tracks
position, motion, or instantaneous velocity over time.
[0037] In some embodiments, the input device 100 is implemented
with additional input components that are operated by the
processing system 110 or by some other processing system. These
additional input components may provide redundant functionality for
input in the sensing region 120, or some other functionality. FIG.
1 shows buttons 130 near the sensing region 120 that can be used to
facilitate selection of items using the input device 100. Other
types of additional input components include sliders, balls,
wheels, switches, and the like. Conversely, in some embodiments,
the input device 100 may be implemented with no other input
components.
[0038] In some embodiments, the input device 100 comprises a touch
screen interface, and the sensing region 120 overlaps at least part
of an active area of a display screen. For example, the input
device 100 may comprise substantially transparent sensor electrodes
overlaying the display screen and provide a touch screen interface
for the associated electronic system. The display screen may be any
type of dynamic display capable of displaying a visual interface to
a user, and may include any type of light emitting diode (LED),
organic LED (OLED), cathode ray tube (CRT), liquid crystal display
(LCD), plasma, electroluminescence (EL), or other display
technology. The input device 100 and the display screen may share
physical elements. For example, some embodiments may utilize some
of the same electrical components for displaying and sensing. As
another example, the display screen may be operated in part or in
total by the processing system 110.
[0039] It should be understood that while many embodiments of the
invention are described in the context of a fully functioning
apparatus, the mechanisms of the present invention are capable of
being distributed as a program product (e.g., software) in a
variety of forms. For example, the mechanisms of the present
invention may be implemented and distributed as a software program
on information bearing media that are readable by electronic
processors (e.g., non-transitory computer-readable and/or
recordable/writable information bearing media readable by the
processing system 110). Additionally, the embodiments of the
present invention apply equally regardless of the particular type
of medium used to carry out the distribution. Examples of
non-transitory, electronically readable media include various
discs, memory sticks, memory cards, memory modules, and the like.
Electronically readable media may be based on flash, optical,
magnetic, holographic, or any other storage technology.
[0040] FIG. 2 is a partial schematic plan view of the input device
100 of FIG. 1 in accordance with embodiments of the invention. The
input device 100 includes an array of sensing elements 150 and a
processing system 110. In some embodiments, the circuitry that
comprises the processing system 110 is embodied as a single
integrated chip (IC) or as multiple IC's. While the processing
system 110 illustrated in FIG. 2 includes one IC, the processing
system 110 may be implemented with more ICs to control the various
components in the input device. For example, the functions of the
IC of the processing system 110 may be implemented in more than one
integrated circuit that can drive transmitter signals and/or
receive resulting signals received from the array of sensing
elements 150. In embodiments where there is more than one IC of the
processing system 110, communications between separate processing
system 110 ICs may be achieved through a synchronization mechanism,
which sequences the signals provided to the transmitter electrodes
210. In some embodiments, the synchronization mechanism may be
internal to any one of the ICs.
[0041] The array of sensing elements 150 includes a plurality of
first electrodes 210 (e.g., 210-1, 210-2, 210-3, etc.) and a
plurality of second electrodes 220 (e.g., 220-1, 220-2, 220-3,
etc.). The first electrodes 210 and second electrodes 220 may be
referred to herein collectively as "sensor electrodes." In some
embodiments, the first electrodes 210 are perpendicular, or
approximately perpendicular, to the second electrodes 220.
Additionally, although the first electrodes 210 are illustrated in
FIG. 2 as being wider than the second electrodes 220, in various
embodiments, the width of the first electrodes 210 may be
approximately equal to, or smaller than the width of the of the
second electrodes 220.
[0042] First electrodes 210 and second electrodes 220 are ohmically
isolated from each other by one or more insulators composed of
electrically insulative material which separate the first
electrodes 210 from the second electrodes 220 and prevent them from
electrically shorting to each other. The electrically insulative
material separates the first electrodes 210 and the second
electrodes 220 at cross-over areas at which the electrodes
intersect. In one configuration, the first electrodes 210 and/or
second electrodes 220 are formed with jumpers connecting different
portions of the same electrode. In other configurations, the first
electrodes 210 and the second electrodes 220 are separated by one
or more layers of electrically insulative material. In yet other
configurations, at least some of the first electrodes 210 and
second electrodes 220 may be disposed on a single layer, with no
jumpers.
[0043] In some touch screen embodiments, the first electrodes 210
comprise one or more common electrodes (e.g., "V-corn electrodes")
used in updating the display of a display screen. In other
embodiments, the second electrodes 220 comprise one or more common
electrodes (e.g., "V-corn electrodes") used in updating the display
of the display screen. In further embodiments, the first electrodes
210 and second electrodes 220 comprise one or more common
electrodes (e.g., "V-corn electrodes") used in updating the display
of the display screen. Further, in various embodiments the first
electrodes 210 and/or second electrodes 220 comprise the entire
Vcom electrode (common electrode(s)). These common electrodes may
be disposed on an appropriate display screen substrate. For
example, the common electrodes may be disposed on the TFT glass in
some display screens (e.g., in-plane switching (IPS) or
plane-to-line switching (PLS)), on the bottom of the color filter
glass of some display screens (e.g., patterned vertical alignment
(PVA) or multi-domain vertical alignment (MVA)), a glass substrate
of an organic light emitting diode (OLED), etc. In such
embodiments, the common electrode can also be referred to as a
"combination electrode," since it performs multiple functions. In
various embodiments, two or more first electrodes 210 or second
electrodes 220 may share one or more common electrodes.
[0044] The first electrodes 210 and/or second electrodes 220 may be
formed as discrete geometric forms, polygons, bars, pads, lines or
other shape, which are ohmically isolated from one another. The
first electrodes 210 and/or second electrodes 220 may be
electrically coupled through circuitry to form electrodes having
larger plan area relative to a discrete one of the first electrodes
210 and/or second electrodes 220. The first electrodes 210 and/or
second electrodes 220 may be fabricated from opaque or non-opaque
conductive materials. In embodiments wherein the first electrodes
210 and/or second electrodes 220 are utilized with a display
device, it may be desirable to utilize non-opaque conductive
materials for the first electrodes 210 and/or second electrodes
220. In embodiments wherein the first electrodes 210 and/or second
electrodes 220 are not utilized with a display device, it may be
desirable to utilize opaque conductive materials having lower
resistivity for the first electrodes 210 and/or second electrodes
220 to improve sensor performance. Materials suitable for
fabricating the first electrodes 210 and/or second electrodes 220
include Indium Tin Oxide (ITO), aluminum, silver, copper, and
conductive carbon materials, among others. The first electrodes 210
and/or second electrodes 220 may be formed as contiguous body of
conductive material having little or no open area (La, having a
planar surface uninterrupted by holes), or may alternatively be
fabricated to form a body of material having openings formed
therethrough. For example, the first electrodes 210 and/or second
electrodes 220 may be formed a mesh of conductive material, such as
a plurality of interconnected thin metal wires.
[0045] The first electrodes 210 and second electrodes 220 may be
referred to herein as "sensor electrodes." For example, first
electrodes 210 may be referred to herein as "first sensor
electrodes," and second electrodes 220 may be referred to herein as
"second sensor electrodes." Sensor electrodes may also be used
herein to refer to any combination of first electrodes 210 and/or
second electrodes 220.
[0046] In one embodiment, the processing system 110 includes a
sensor module 240 and a noise reduction module 265. In other
embodiments, the processing system 110 also includes a
determination module, a display module, and a memory. The
processing system 110 is coupled to the first electrodes 210
through a first plurality of conductive routing traces 255 and to
the second electrodes 220 through a second plurality of conductive
routing traces 257.
[0047] The sensor module 240 drives the array of sensing elements
150 for capacitive sensing to detect the presence and position of
input objects 140 within sensing region 120. The processing system
110 determines position locations based on signals received by the
sensor module 240. In embodiments that include a determination
module, these determinations are made by the determination module.
The processing system 110 also stores location information about
input objects detected in previous "capacitive frames", including
signals received in the absolute sensing mode and the
transcapacitive sensing mode. The term "object location data" as
used herein refers to data that identifies a location at which the
processing system 110 has deemed that an input object exists 140.
In some embodiments, the stored information is stored in a memory.
In embodiments that include a display, processing system 110 drives
display elements with signals to update a displayed image. In some
embodiments, a display module included in the processing system 110
drives the display elements. The noise reduction module 265
performs operations to reduce the impact of noise on signals
received with the sensor electrodes.
[0048] The sensor module 240 is able to drive the array of sensing
elements 150 for capacitive sensing in two different modes: an
absolute sensing mode, which is based on self-capacitance (also
known as absolute capacitance), and a transcapacitive mode, which
is based on trans-capacitance (also known as a mutual
capacitance).
[0049] In the absolute sensing mode, the sensor module 240 drives
the first electrodes 210 and receives, with the first electrodes
210, first signals indicative of capacitive coupling between the
first electrodes 210 and an input object 140 present in the sensing
region 120, if any. The sensor module 240 also drives the second
electrodes 220 and receives, with the second electrodes 220, second
signals indicative of capacitive coupling between the second
electrodes 220 and an input object 140 present in the sensing
region 120. The processing system 110 analyzes the first signals
and second signals to determine the location of the input object
140. More specifically, the processing system 110 determines one or
more locations within the sensing region 120 that are associated
with both first signals and second signals that have an intensity
that is greater than a threshold. Each first electrode 210 is
associated with a particular vertical location within the sensing
region 120. Similarly, each second electrode 220 is associated with
a particular horizontal location within the sensing region 120.
Thus, a location within the sensing region is generally associated
with one or more first electrodes 210 that have similar vertical
locations as the location and one or more second electrodes 220
that have similar horizontal locations as the location. The
processing system 110 determines that an input object 140 is at a
particular location if both the first signal for that location and
the second signal for that location are above a threshold.
[0050] In the transcapacitive mode, the sensor module 240 drives
the first electrodes 210 with transmitter signals and receives
resulting signals with the second electrodes 220. Alternatively,
the sensor module 240 may drive the second electrodes 220 with
transmitter signals and receive resulting signals with the first
electrodes 210. In either case, the electrode that is transmitted
with may be referred to herein as a "transmitter electrode" or
"transmitter sensor electrode" and the electrode that is received
with may be referred to herein as a "receiver electrode" or
"receiver sensor electrode." The resulting signals received are
indicative of capacitive coupling between the first electrodes 210
and the second electrodes 220. The areas of localized capacitive
coupling between transmitter electrodes and receiver electrodes may
be termed "capacitive pixels." The capacitive coupling between the
transmitter electrodes and receiver electrodes changes with the
proximity and motion of input objects in the sensing region 120
associated with the transmitter electrodes and the receiver
electrodes. The sensor module 240 may be configured to pass the
resulting signals to a determination module for determining the
presence of an input object and/or to a memory for storage. In
various embodiments, the IC of the processing system 110 may be
coupled to drivers for driving the first electrodes 210 and/or
second electrodes 220. The drivers may be fabricated using
thin-film-transistors (TFT) and may comprise switches,
combinatorial logic, multiplexers, and other selection and control
logic.
[0051] Transmitter electrodes may be operated such that one
transmitter electrode transmits at one time, or multiple
transmitter electrodes transmit at the same time. Where multiple
transmitter electrodes transmit simultaneously, these multiple
transmitter electrodes may transmit the same transmitter signal and
effectively produce an effectively larger transmitter electrode, or
these multiple transmitter electrodes may transmit different
transmitter signals. For example, multiple transmitter electrodes
may transmit different transmitter signals according to one or more
coding schemes that enable their combined effects on the resulting
signals of receiver electrodes to be independently determined. The
transmitter electrodes may transmit transmitter signal bursts.
Transmitter signal bursts may include multiple transmitter signal
cycles (e.g., 20-40 bursts). The number of bursts in a particular
transmitter signal is referred to herein as a burst count.
Typically, two or more transmitter signal bursts may be transmitted
for each row for each capacitive frame.
[0052] The receiver electrodes may be operated singly or multiply
to acquire resulting signals. The resulting signals may be used to
determine measurements of the capacitive couplings at the
capacitive pixels.
[0053] In the transcapacitive mode, a set of measurements from the
capacitive pixels form a "capacitive image" representative of the
capacitive couplings at the pixels. Multiple capacitive images may
be acquired over multiple time periods, and differences between
them used to derive information about input in the sensing region.
For example, successive capacitive images acquired over successive
periods of time can be used to track the motion(s) of one or more
input objects entering, exiting, and within the sensing region.
Further, the multiple capacitive images may be stored in a memory
when obtained. In the absolute sensing mode, a set of measurements
forms a set of profiles.
[0054] The background capacitance of the input device 100 is the
capacitive image associated with no input object in the sensing
region 120. The background capacitance changes with the environment
and operating conditions, and may be estimated in various ways. For
example, some embodiments take "baseline images" when no input
object 140 is determined to be in the sensing region 120, and use
those baseline images as estimates of their background
capacitances. That is, some embodiments compare the measurements
forming a capacitance image with appropriate "baseline values" of a
"baseline image" associated with those pixels, and determine
changes from that baseline image.
[0055] In some situations, the baseline image may be "relaxed."
Baseline relaxation refers to a transition from one baseline
capacitive image to another baseline capacitive image. More
specifically, the processing system 110 updates the baseline image
based on recently-received measurements, to account for any changes
in the baseline image that may have occurred since previously
recording a baseline image. In some embodiments, the baseline image
is relaxed periodically.
[0056] Environmental noise may affect the signals received by the
sensor module 240 when the sensor module 240 is driving the array
of sensing elements 150 for capacitive sensing. More specifically,
various noise signals, such as ambient signals or signals generated
by various elements of the input device 100, may contribute to
resulting signals in transcapacitive mode or to the signals
received in the absolute sensing mode. These noise-corrupted
signals may cause input device 100 to falsely identify a presence
of one or more input objects. Falsely detected input objects are
referred to herein as "ghost objects."
[0057] In order to reduce the effect of noise on the results
generated by the input device 100, the processing system 110
operates the sensor electrodes in a noise detection mode. The noise
reduction module 265 in the processing system 110, which may
include appropriate hardware and/or software components for the
operations described, may perform operations associated with the
noise detection mode. More specifically, the noise reduction module
265 may perform noise reduction operations after sensor module 240
has driven the sensor electrodes for capacitive sensing. Operations
described below as being performed by the processing system 110 and
that are related to the noise reduction operations may
alternatively be performed by the noise reduction module 265.
[0058] In the noise detection mode, the processing system 110
performs a series of steps to reduce the impact of noise as
compared with a system that does not operate in a noise detection
mode. The series of steps includes performing sensing in absolute
sensing mode, predicting an input object 140 location based on data
from previous capacitive frames, performing sensing in
transcapacitive mode, determining the position of an input object
140 based on the sensing in transcapacitive mode, correlating the
absolute mode results, the transcapacitive mode results, and the
prediction results, rejecting object location data (i.e., data
including a location that was falsely identified as including an
input object 140) and entering a high noise mode based on the
results of the correlation, and preparing final results data for
transmission to the electronic device. The final results data is
referred to as an "object locations report" herein and includes
object location data for input objects 140 sensed in the sensing
region 120 and may optionally exclude falsely identified locations.
The object location data include locations for which an object is
determined to exist. Thus, the object location data stored in the
object locations report includes a set of locations at which input
objects have been detected.
[0059] In the step of performing the absolute mode sensing, the
sensor module 240 performs absolute sensing as described above.
Thus, the sensor module 240 drives the first electrodes 210 in an
absolute sensing mode and receives signals with the first
electrodes 210 and drives the second electrodes 220 in an absolute
sensing mode and receives signals with the second electrodes 220.
The results from the absolute sensing mode comprise "absolute
sensing results," which include "object location data"--data
indicating locations in the sensing region 120 at which input
objects 140 are determined to exist. These object location data
generally comprise locations for which the signal strengths for the
corresponding first electrode 210 and second electrode 220 are
above a particular threshold (a "sensing threshold"). For example,
if a first sensor 210 corresponding to a particular vertical
coordinate has a signal strength above a particular threshold and a
second sensor 220 corresponding to a particular horizontal
coordinate has a signal strength above a particular threshold, then
the location having the same horizontal coordinate as the first
sensor 210 and the same vertical coordinate as the second sensor
220 would be included as object location data in the absolute
sensing results.
[0060] In the prediction step, the processing system 110 examines
information for previous capacitive frames and attempts to generate
a predicted location of an input object 140 based on the stored
information. In some embodiments, prediction is done by matching
movements of an input object 140 detected in one or more previous
capacitive frames to a set of known movements (i.e., matching a
pattern of movements to the stored information). In some
embodiments, one known movement is a swipe, which comprises an
input object moving approximately linearly within the sensing
region 120. Other known movements include tapping (e.g., repeatedly
placing and removing an input object at a particular location), and
drumming (e.g., a first object appearing and disappearing at a
first location and then a second object appearing and disappearing
at a second location, repeated in succession). When a particular
pattern is recognized, the processing system 110 generates one or
more predicted object location data, which include locations within
the sensing region 120 at which objects are predicted to exist. The
processing system 110 may generate multiple predicted locations
based on the information stored. The predicted locations generated
for a particular capacitive frame comprise prediction results.
[0061] In the transcapacitive sensing step, the sensor module 240
performs transcapacitive sensing as described above. More
specifically, the sensor module 240 drives transmitter signals onto
a transmitter electrode and receives resulting signals with a
receiver electrode. The sensor module 240 performs sensing in this
way for a particular location by driving a transmitter electrode
and receiving with a receiver electrode where the intersection of
the transmitter electrode and receiver electrode are at the
location for sensing. In some embodiments, the sensor module 240
scans locations corresponding to the entire sensing region 120. In
some embodiments, the sensor module 240 does not scan the entire
sensing region 120 in transcapacitive mode but only scans regions
within the vicinity of the locations of objects detected in the
absolute sensing mode or predicted to exist in the prediction step.
In other words, in some embodiments, the sensor module 240 scans
sensor electrodes for which the received signal in the absolute
sensing mode satisfies the sensing threshold or for which an object
is predicted to exist, but does not scan sensor electrodes for
which the received signal in the absolute sensing mode do not
satisfy the sensing threshold or for which an object is predicted
to exist. If the sensor module 240 scans less than the entire
sensing region 120, then the sensor module 240 may increase the
burst count for transcapacitive scans conducted relative to a
"commonly used burst count," which is the burst count that is used
when the sensor module 240 is in normal sensing mode (i.e., when
the sensor module 240 is conducting transcapacitive sensing and has
not determined that the burst count should be increased).
[0062] In the input object location calculation step, the
processing system 110 determines locations within the sensing
region 120 at which an input object 140 is present based on the
results of the transcapacitive sensing. To do this, the processing
system 110 determines which resulting signals cross a threshold. If
the resulting signal for a particular location crosses a threshold,
then the processing system 110 deems an input object 140 to be at
that location. The result of the input object 140 calculation step
is a set of transcapacitive sensing results. These results comprise
the locations for which corresponding transcapacitive signals cross
a particular threshold. The threshold may be constant, dynamically
determined, or configurable.
[0063] In the correlation step, the processing system 110
correlates the object location data determined in the absolute
sensing step and the object location data predicted in the
prediction step with the object location data generated in the
transcapacitance step. More specifically, the processing system 110
attempts to match each location of a detected input object in the
absolute sensing results and each location of a detected input
object in the prediction results with the locations of detected
input objects in the transcapacitive sensing results. If a location
for an object that is included in either the absolute sensing
results or the prediction results is not present in the
transcapacitive data, then the object location data is disregarded
(i.e., not included in the object locations report). Similarly, if
object location data is present in the transcapacitive sensing
results that is not included in either the absolute sensing results
or the prediction results, then that object location data is
disregarded (i.e.; not included in the object locations report).
The results from the correlation step include all object location
data included in either the absolute sensing results or the
prediction results and also included in the transcapacitive sensing
results. These results are referred to herein as the "correlation
results." These correlation results are included in the object
locations report, which may later be modified by the high noise
mode; as described below.
[0064] If object location data is disregarded in this way, then the
processing system 110 enters a high noise mode, after which the
processing system 110 prepares the object locations report and
transmits that report to the electronic device. If no object
location data is disregarded in this way, then the processing
system 110 does not enter a high noise mode and instead proceeds
directly to generate the report and transmit the report.
[0065] The report generated ("object locations report") includes
data regarding the locations at which input objects are deemed to
exist based on the absolute sensing step, data regarding the
locations at which input objects are deemed to exist based on the
prediction step, and data regarding the locations at which input
objects are deemed to exist based on the transcapacitive step, as
modified by both the correlation step, and, if conducted, by the
high noise mode step. More specifically, if the high noise mode
step is not performed, then the report generated includes all of
the locations in the transcapacitive sensing results (which are the
same as the results in the prediction results and the absolute
sensing results, since all object location data matched in the
correlation step). If the high noise mode is performed, then the
report includes the locations in the transcapacitive sensing
results, the absolute sensing results, and the prediction results,
as modified by the correlation step, and also as modified by the
high noise mode step. The high noise mode is now described in more
detail.
[0066] In one or more embodiments, the high noise mode is a mode in
which the processing system 110 analyzes data stored (e.g., in a
memory) about sensing results from previous capacitive frames and
modifies the object locations report based on the stored data from
the previous frames. In the high noise mode, the processing system
110 may perform one or more operations to modify locations in the
object locations report. Such operations may include one or more of
the following: removing object locations data for which a
corresponding object is not detected in at least a threshold number
of previous capacitive frames; removing object locations data for
probable duplicate input objects: removing object locations data
for input objects determined to have previously "left" the sensing
region 120 for a threshold number of capacitive frames; performing
a smoothing operation based on the data stored; adding object
locations data for input objects 140 that were previously detected
for a threshold number of frames; and suspending baseline
relaxation. These operations are now described in more detail.
[0067] For the operation to remove objects not detected in at least
a threshold number of previous capacitive frames, for each location
in the sensing region 120 for which object location data is
included in the object locations report, the processing system 110
determines if an input object 140 corresponding to that location
has been detected in at least a threshold number of previous
capacitive frames. The threshold for the threshold number may be
dynamically determined, configurable, or constant. A dynamic
determination may be based on the noise levels. As the noise level
increases, the processing system 110 may also increase the
threshold. The processing system 110 may map different noise levels
to different thresholds. Configurable thresholds may be configured
during configuration of the processing system 110. A configured
threshold may be based on a predicted noise level for the device,
balanced against a desired maximum level of lag, as increasing the
threshold also increases the level of lag. A constant threshold is
a threshold that remains constant and that is based on empirical
data. If no input object 140 corresponding to that location was
detected in at least the threshold number of previous capacitive
frames, then the processing system 110 removes the object location
data corresponding to that location from the object locations
report. If an input object 140 corresponding to that location was
detected in at least the threshold number of previous capacitive
frames, then the processing system 110 does not remove any object
location data. In some embodiments, processing system 110
identifies an object as being the same object in different
capacitive frames based on similarities in number and location of
object locations included in the previous capacitive frames. For
example, if data for a single object location is included for one
capacitive frame and data for another single object location is
included for an immediately prior capacitive frame and the first
object location is near to the second object location, then the
processing system may deem that the first object location data and
second object location correspond to the same input object 140.
[0068] For the operation consisting of removing probable
duplicates, the processing system 110 examines the object locations
data stored to determine whether a "duplicate" object is detected
in the current frame. A duplicate object is detected if signals
received with a single sensor electrode cause two instances of
object detection to occur. This situation can happen in absolute
sensing mode if, for example, a signal for a particular first
electrode 210 is above a threshold and signals for two different
second electrodes 220 are both above a threshold. In such a
situation, objects would be deemed to be detected at the
intersection between the first electrode and the two second
electrodes 220. Both object would be detected based on signals
received with a single electrode (the first electrode 210).
[0069] If signals received with a single sensor electrode cause two
or more instances of object detection to occur, then the processing
system 110 deems one of those detected input objects to be a
duplicate. If signals received with a single sensor electrode do
not cause two or more instances of object detection to occur, then
the processing system 110 does not deem any detected object to be a
duplicate. In some embodiments, the processing system 110 simply
disregards the object location deemed to be a duplicate. Again,
disregarding the object locations means not including the
corresponding object location data in the object locations report.
In some embodiments, a first object location is deemed to be a
duplicate if the first object location appears after (i.e. in a
later capacitive frame) a second object location. In some
embodiments, the object location that is deemed to be a duplicate
is not outright disregarded, but instead the processing system 110
increases the detection threshold for the object location that is
deemed to be a duplicate. In other words, the processing system 110
increases the signal threshold for the signal corresponding to the
object location. If the corresponding signals for transcapacitance
and absolute sensing are above this increased threshold, then the
object location that is deemed to be a duplicate is reported and
not disregarded. If the signal is below this increased threshold,
then the object location is disregarded. In some embodiments, if
the object location deemed to be a duplicate exists for a threshold
number of capacitive frames, then the object location is no longer
deemed to be a duplicate and is reported to the electronic device.
If the object location exists for less than the threshold number of
capacitive frames, then the object location is still deemed to be a
duplicate.
[0070] For the operation for removing objects that had previously
left the sensing region 120 for a threshold number of frames, the
processing system 110 disregards object locations sensed within a
threshold number of capacitive frames after another object has left
that same location. Processing system 110 only disregards such
object locations if the sensed object location and the object that
has left are sensed with the same pair of first electrode 210 and
second electrode 220. The threshold number of capacitive frames may
be preset, configurable, or dynamically adjusted, as described
above.
[0071] For the smoothing operation, processing system 110 applies a
smoothing calculation to the data stored for previous capacitive
frames in conjunction with the data measured for the current
capacitive frame (which includes the signals received in response
to performing absolute sensing and/or transcapacitive sensing). In
various embodiments, the smoothing calculation may consist of an
averaging function applied to the object location data stored for
previous capacitive frames and detected for the current capacitive
frame, or an averaging function applied to the object location data
stored for most recent capacitive frames and detected for the
current capacitive frame. Further, the smoothing calculation may
consist of an averaging function applied for each object location
in the current capacitive frame, and applied to that location and
locations in the vicinity of that object location. In various
embodiments, smoothing calculations other than averaging may be
applied. For example, interpolation or curve fitting may be
applied. The smoothing calculations are applied to the positional
information for the object locations stored and for the current
capacitive frame.
[0072] For the object adding operation, the processing system 110
adds object location data into the object locations report if an
object was detected in a threshold number (which may be constant,
configurable, or dynamically adjusted, as described above) of
previous capacitive frames but not in the current capacitive frame.
To determine that an object was detected in a threshold number of
previous capacitive frames, the processing system 110 examines the
stored data. If an object is detected within a certain area of the
sensing region 120 (that may be less than the entire sensing region
and may include, for example, the area around a specific
intersection of a first electrode 210 and a second electrode 220)
for a threshold number of frames, then an object corresponding to
that object location is deemed to have been detected for a
threshold number of previous capacitive frames. If no object is
detected in this manner, then no object location data is added to
the object locations report.
[0073] For the suspend baseline relaxation operation, the
processing system stops periodic relaxation of the baseline image.
As described above, baseline relaxation refers to adjusting the
baseline image based on recently-taken capacitive measurements.
When in the high noise mode, the processing system 110 may suspend
periodic baseline relaxation until the high noise mode has
ended.
[0074] After the processing system 110 generates the object
locations report and transmits the report to the electronic device,
sensing for the current capacitive frame is over, and the
processing system 110 begins again at the first step (the absolute
mode sensing step) for the next capacitive frame. The processing
system 110 also stores the absolute sensing results, the prediction
results, and the transcapacitive sensing results for use in later
capacitive frames. If the processing system 110 entered the high
noise mode for the current capacitive frame, then the processing
system 110 leaves the high noise mode when the next capacitive
frame begins.
[0075] FIG. 3 illustrates input object locations sensed in the
sensing region 120 during the absolute sensing mode, the prediction
mode, and the transcapacitive sensing mode, for a particular
capacitive frame, according to an embodiment. An input object 140
is present within sensing region 120, which causes processing
system 110 to detect object at location 302. A processing system
110 conducting absolute sensing would detect the object at object
location 302 because vertical absolute sensing measurements 304 and
horizontal absolute sensing measurements 306 indicate the presence
of such an object. More specifically, the vertical absolute sensing
measurements 304 include a signal strength above a vertical
threshold 308 at a first vertical location 310, and the horizontal
sensing measurements 306 include a signal strength above a
horizontal threshold 314 at a first horizontal location 312. While
processing system 110 would correctly determine the position of an
input object 140 at the location 302, the processing system 110
would also detect the presence of ghost objects 320. Processing
system 110 would detect ghost objects 320 because noise has caused
corresponding vertical signals 322 to exceed the vertical threshold
308. Thus, two ghost objects 320 are detected, located where the
vertical signals 322 that exceed the vertical threshold 308
intersect with the horizontal sensing measurement 306 that exceeds
the threshold 314. With the techniques described above, the ability
to correctly identify ghost objects is increased, and
correspondingly, the number of ghost objects potentially included
in the data report to the electronic device is reduced, thereby
increasing the accuracy of the input device 100.
[0076] FIG. 4 illustrates a prediction operation, according to one
embodiment. For simplicity, only first electrodes 210 are depicted.
The prediction operation is shown over a series of capacitive
frames 402. In the first capacitive frame 402(1), a signal at first
electrode 210(1) is above a threshold and therefore, an object is
deemed to exist at a particular location based on that signal. In
the second capacitive frame 402(2), a signal at a second electrode
210(2) is above a threshold and an object is deemed to exist at a
particular location based on that signal. In the third capacitive
frame, an object is deemed to exist based on a signal associated
with the third electrode 210(3). At the fourth capacitive frame
402(4), the processing system 110 predicts that an object
associated with fourth electrode 210(4) exists, because of the
pattern observed in the previous three capacitive frames. More
specifically, the processing system 110 observed that an object
moved from left to right with a velocity of one electrode 210 per
frame and therefore calculates that in the fourth capacitive frame,
an object associated with the fourth electrode 210(4) would exist
at the location associated with the fourth electrode 210(4).
[0077] FIG. 5 is a flow chart of a method 500 for operating sensor
electrodes in a noise detection node, according to an embodiment.
Although the method steps are described in conjunction with FIGS.
1-4, persons skilled in the art will understand that any system
configured to perform the method steps, in various alternative
orders, falls within the scope of the present invention.
[0078] The method 500 begins at step 502, where processing system
110 performs sensing in absolute sensing mode. As described above,
in absolute sensing mode, the sensor module 240 drives first
electrodes 210 in an absolute sensing mode and receives signals
with the first electrodes 210. The sensor module 240 also drives
second electrodes 220 in an absolute sensing mode and receives
signals with the second electrodes 220. Input objects 140 are
deemed to exist at locations corresponding to a first electrode 210
for which a signal is above a threshold and a second electrode 220
for which a signal is above a threshold. The signals received
comprise absolute sensing results. The processing system 110
records these absolute sensing results for later analysis.
[0079] At step 504, the processing system 110 performs a prediction
step. As described above, the processing system 110 examines stored
object location data and attempts to recognize a pattern in that
object location data. More specifically, the processing system 110
attempts to find a series of locations at which objects are
detected that match a particular known pattern such as swiping,
tapping, or drumming. If a particular pattern is recognized, then
the processing system 110 deems that a particular location is
predicted to have an input object 140, and records that location as
a predicted object location. If no such pattern is recognized, then
the processing system 110 does not deem that any location is
predicted to have an input object 140.
[0080] At step 506, the processing system 110 performs sensing in
transcapacitive sensing mode. More specifically, the sensor module
240 drives transmitter signals onto a transmitter electrode and
receives resulting signals with a receiver electrode. In some
embodiments, the sensor module 240 performs transcapacitive sensing
for each transmitter electrode-receiver electrode pair to determine
capacitive characteristics for locations that span the entire
sensing region 120.
[0081] At step 508, the processing system 110 analyzes the
resulting signals received during transcapacitive sensing to
determine locations for input objects 140 in the sensing region
120, if any. If a resulting signal received for a particular
transmitter electrode-receiver electrode pair satisfies a
threshold, then an input object 140 is deemed to be detected at the
location associated with that transmitter electrode-receiver
electrode pair. If a resulting signal does not satisfy a threshold,
then an input object 140 is to be not detected at the location
corresponding to the resulting signal.
[0082] At step 510, the processing system 110 determines whether
there are any object location mismatches. An object location
mismatch occurs if an object location in either the absolute
sensing results or the prediction results is not present in the
transcapacitive data. An object location mismatch also occurs if an
object location is present in the transcapacitive sensing results
that is not included in either the absolute sensing results or the
prediction results, then that object location is disregarded. If an
object location mismatch occurs, then the method 500 proceeds to
step 512. If an object location mismatch does not occur, then the
method 500 proceeds to step 516.
[0083] At step 512, the processing system 110 disregards mismatched
object locations. Disregarding object locations means not including
those object locations in the detected object location data that is
reported to the electronic device.
[0084] At step 514, the processing system 110 performs a high noise
mode. A high noise mode is a mode in which the processing system
110 analyzes data stored (e.g., in a memory) about object locations
detected in previous capacitive frames and modifies the data stored
in the object locations report based on the stored data from the
previous frames. In high noise mode, the processing system 110 may
perform one or more operations to modify locations in the object
locations report. Such operations may include the following:
removing objects not detected in at least a threshold number of
previous capacitive frames: removing probable duplicates; removing
object location data for input objects 140 that had previously
"left" the sensing region 120 for a threshold number of capacitive
frames; performing a smoothing operation based on the data stored
in a memory; adding objects that were previously detected for a
threshold number of frames; and suspending baseline relaxation.
These operations are described above in more detail.
[0085] At step 516, the processing system 110 transmits a report to
the electronic device, where the transmitted report includes the
object locations detected and not excluded in the disregard step
(512). At step 518, the processing system 110 proceeds to the next
capacitive frame and returns to step 502.
[0086] The embodiments and examples set forth herein were presented
in order to best explain the embodiments in accordance with the
present technology and its particular application and to thereby
enable those skilled in the art to make and use the invention.
However, those skilled in the art will recognize that the foregoing
description and examples have been presented for the purposes of
illustration and example only. The description as set forth is not
intended to be exhaustive or to limit the invention to the precise
form disclosed.
[0087] In view of the foregoing, the scope of the present
disclosure is determined by the claims that follow.
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